Throughout this application, various references are referred to by abbreviation. Disclosures of these publications in their entireties are hereby incorporated by references into this application to more fully describe the state of the art to which this invention pertains. Full bibliographic citation for these references may be found at the end of the specification, preceding the claims.
The cellular interactions that control the differentiation of dorsal cell types form neural progenitors have been examined in neural plate explants. Certain genes that are expressed in the dorsal neural tube are initially expressed uniformly within the neural plate and appear to achieve their dorsal restriction through a Sonic Hedgehog (SHH)-mediated repressive signal from the notochord. The acquisition of definitive dorsal cell fates, however, requires a contact-dependent signal from the epidermal ectoderm. BMP-4 and BMP-7 are expressed in the epidermal ectoderm and both proteins mimic its inductive activity. BMP-4 and a related gene, Dsl-1, are subsequently expressed by cells in the dorsal neural tube, indicating that the early dorsalizing activity of the epidermal ectoderm is later acquired by neural cells. The differentiation of dorsal cell types, therefore, appears to be initiated at the neural plate stage and to involve the opponent activities of a BMP-mediated dorsalizing signal from the epidermal ectoderm and a SHH-mediated ventralizing signal from the notochord.
The diverse neuronal and glial cell types generated during the development of the vertebrate nervous system derive from a simple columnar epithelium, the neural plate. The differentiation of distinct cell types from neural plate progenitors is thought to be controlled by the actions of secreted inductive factors (Smith, 1994; Johnson and Tabin, 1995). Cell types generated from the medial region of neural plate (notably floor plate cells and motor neurons) populate the ventral half of the neural tube and are induced by Sonic Hedgehog (SHH), a secreted glycoprotein that is synthesized by axial mesodermal cells of the notochord (Echelard et al, 1993; Krauss et al., 1993; Ericson et al., 1995; Marti et al., 1995; Roelink et al., 1994, 1995; Tanabe et al., 1995). Elimination of the notochord prevents the differentiation of floor plate cells and motor neurons (van Straaten and Hekking, 1991: Yamada et al., 1991; Ericson et al, 1992) establishing that a signal from the notochord, presumably SHH, is required for the differentiation of ventral cell types.
Cell types derived from the lateral region of the neural plate which populate the dorsal half of the neural tube (neural crest cells, dorsal commissural neurons and roof plate cells) are able to differentiate in the absence of notochord-derived signals (Yamada et al., 1991; Ericson et al., 1992; Tremml et al., unpublished data). Moreover, in the absence of the notochord certain genes that are normally restricted to dorsal regions of the neural tube are expressed at all dorsoventral levels (Yamada et al., 1991, Basler et al., 1993; Goulding et al, 1993). These observations raise the issue of how the dorsal fates of neural plate cells are acquired. One possibility is that neural plate cells are predisposed to differentiate into dorsal cell types unless exposed to a ventralizing signal from the notochord. Alternatively, the acquisition of dorsal fates might require the action of inductive signals that originate from adjacent tissues. Evidence for the existence of dorsalizing signals has derived from the analysis of neural crest cell differentiation. Epidermal ectoderm cells that flank the neural plate and mesodermal cells that underly the lateral border of the neural plate have each been proposed as sources of signals that induce neural crest cells (Moury and Jacobson, 1989, 1990; Takada et al., 1994; Dickinson et al., 1995; Selleck and Bronner-Fraser, 1995; Mayor et al., 1995; de la Torre and Tessier-Lavigne, unpublished data). Neural crest cells can be induced in vitro by exposure of neural plate explants to Dorsalin-1 (Dsl-1), a TGF(-related factor (Kingsley, 1994) expressed in the dorsal region of the neural tube (Basler et al., 1993). Dsl-1 is, however, not expressed in the epidermal ectoderm and appears in the neural tube only after neural crest cells have been specified (Basler et al., 1993; Nieto et al., 1994; Nakagawa and Takeichi, 1995) indicating that Dsl-1 is not involved in the initial steps of neural crest cell differentiation. Thus, the cellular interactions that initiate the dorsal differentiation of neural plate cells and the molecular identity of relevant inducing factors remain uncertain.
In the present studies applicants have analyzed the interactions that specify the dorsal fate of neural plate cells using an in vitro assay of cell differentiation in neural plate explants. Applicants first examined whether neural plate cells are predisposed to dorsal fates or whether inductive signals from adjacent cells are required. Applicants"" results show that certain genes that characterize the dorsal neural tube are initially expressed by all neural plate cells and achieve their dorsal restriction through a SHH-mediated repressive signal from the notochord. The acquisition of definitive dorsal cell fates, however, does not occur by default and instead involves a contact-dependent inductive signal from the epidermal ectoderm. Two members of the TGF gene family, BMP-4 and BMP-7, are expressed in the epidermal ectoderm flanking the neural plate and recombinant BMP-4 and BMP-7 mimic the dorsalizing activity of the epidermal ectoderm. The acquisition of dorsal neural fates is, therefore, initiated at the neural plate stage and appears to involve the opponent activities of a BMP-mediated dorsalizing signal from the epidermal ectoderm and a SHH-mediated ventralizing signal from the notochord.
This invention provides a composition for stimulating neural crest cell differentiation comprising an amount of a purified protein selected from a group consisting of bone morphogenetic protein 4, bone morphogenetic protein 5, bone morphogenetic protein 7, dorsalin-1 and combinations thereof effective to stimulate neural crest cell differentiation and an acceptable carrier. This invention also provides methods for stimulating neural crest cell differentiation in a culture comprising administering the above composition to the culture. This invention provides a method for stimulating neural crest cell differentiation in a subject comprising administering to the subject the above composition.
This invention provides a composition for regenerating nerve cells in a subject comprising an amount of a purified protein selected from a group consisting of bone morphogenetic protein 4, bone morphogenetic protein 5, bone morphogenetic protein 7, dorsalin-1and combinations thereof effective to regenerate nerve cells and an acceptable carrier. This invention provides a method for regenerating nerve cells in a subject comprising administering to the subject the above composition.
This invention also provides a composition for promoting bone growth in a subject comprising an amount of the purified protein selected from a group consisting of bone morphogenetic protein 4, bone morphogenetic protein 5, bone morphogenetic protein 7, dorsalin-1 and combinations thereof effective to promote bone growth and an acceptable carrier. This invention further provides methods for promoting bone growth in a subject comprising administering to the subject the above composition.
This invention provides a composition for promoting wound healing in a subject comprising an amount of the purified protein selected from a group consisting of bone morphogenetic protein 4, bone morphogenetic protein 5, bone morphogenetic protein 7, dorsalin-1 and combinations thereof effective to promote wound healing and an acceptable carrier. This invention also provides methods for promoting wound healing in a subject comprising administering to the subject the above composition.
This invention provides a composition for treating neural tumor in a subject comprising an amount of the purified protein selected from a group consisting of bone morphogenetic protein 4, bone morphogenetic protein 5, bone morphogenetic protein 7, dorsalin-1 and combinations thereof effective to inhibit neural tumor cell growth and an acceptable carrier. This invention also provides methods for treating neural tumor in a subject comprising administering to the subject the above composition.